Various types of equipment and procedures are currently used to inspect new tires and used tires. Such inspections are preferably conducted to find hidden irregularities or defects prior to retreading used tire casings. Economic loss occurs from retreading a damaged tire casing and later scrapping the resulting retread tire. Even greater loss may occur from potential safety hazards associated with using a retread tire having a damaged tire casing.
Most modern tires used on trucks and automobiles have multiple steel cords integrally molded within the associated tire casing. Work hardening of the steel cords may occur from operating the associated tire with less than the recommended air pressure. This type of defect in a used tire casing is sometimes referred to as a "zipper." Catastrophic failure may occur from retreading a used tire casing with damaged steel cords. For example, a new tire or a retread tire, after mounting on a tire rim, is often over pressurized to set or seal the associated tire beads within the rim. During over pressurization, catastrophic failure may occur in the vicinity of the damaged steel cords. As a result of such potential hazards, most major fleet tire dealers require inspection of used tire casings prior to retreading.
Although substantial efforts have been made to minimize dust, debris and other contamination associated with retreading used tires, tire inspection equipment must operate in an environment which is less than ideal for modern electronic components. Also, tire inspection equipment is frequently subject to significant mechanical vibration during handling and rotation of used tire casings. Contamination of electronic components and/or damage to electrical wiring and electrical circuits may reduce the overall operating efficiency of some types of tire inspection equipment.
Examples of tire inspection equipment and techniques are shown in U.S. Pat. No. 4,936,138 entitled Method And Apparatus For Tire Inspection and U.S. Pat. No. 4,520,307 entitled High-Voltage Tire Testing Apparatus. For many years Oliver Rubber Company located at P.O. Drawer 1827, Athens, Ga. 30603-1827 has manufactured and sold Tuff-Scan.RTM. and Wide-Scan.RTM. ultrasonic tire casing inspection equipment.